Customized orthodontic bracket system

ABSTRACT

A customized orthodontic bracket system is provided. The system can include a bracket having a customized bracket bonding pad for bonding the bracket to a tooth of a patient and a bracket slot adapted to receive a customized archwire. The customized archwire is adapted to be positioned in the bracket slot to form a precise bracket slot-archwire interface. The bracket slot and the archwire when positioned in the bracket slot can be positioned substantially adjacent the tooth surface to reduce induced vertical error in tooth positioning. The bracket slot can be configured to have a bracket slot width substantially matching a cross-section of the archwire to reduce torque rotation around an axis of the archwire when positioned therein to further enhance end-of-treatment tooth positioning and reduce overall treatment time.

BACKGROUND OF THE INVENTION

1. Related Applications

This patent application is a continuation application which claims thebenefit of and priority to U.S. patent application Ser. No. 13/242,997,filed on Sep. 23, 2011, which claims the benefit of and priority to U.S.patent application Ser. No. 11/522,674, filed on Sep. 18, 2006, now U.S.Pat. No. 8,057,226, which claims the benefit of and priority to U.S.patent application Ser. No. 10/897,149, filed on Jul. 22, 2004, now U.S.Pat. No. 7,850,451, which claims the benefit of and priority toapplication Ser. No. 10/075,676, filed Feb. 13, 2002, now U.S. Pat. No.6,776,614, which are all incorporated by reference herein in theirentirety.

2. Field of the Invention

This invention relates generally to the field of orthodontics. Moreparticularly, the invention relates to orthodontic brackets andarchwires for straightening the teeth of a patient.

DESCRIPTION OF RELATED ART

A widely used method to straighten or align teeth of a patient is tobond brackets onto the teeth and run elastic wires of rectangularcross-sectional shape through the bracket slots. Typically, the bracketsare off-the-shelf products. In most cases, they are adapted to a certaintooth (for instance an upper canine), but not to the individual tooth ofa specific patient. The adaptation of the bracket to the individualtooth is performed by filling the gap between tooth surface and bracketsurface with adhesive to thereby bond the bracket to the tooth such thatthe bracket slot, when the teeth are moved to a finish position, lies inflat horizontal plane. The driving force for moving the teeth to thedesired finish position is provided by the archwire. For lingualbrackets, a system has been developed by Thomas Creekmore that hasvertical bracket slots. This allows an easier insertion of the wire. Thelonger side of the wire is therefore oriented vertically. Unitek hasmarketed this bracket system under the trade name CONSEAL™.

A computerized approach to orthodontics based on design and manufactureof customized brackets for an individual patient, and design andmanufacture of a customized bracket placement jig and archwire, has beenproposed in the art. See U.S. Pat. No. RE 35,169 to Lemchen et al. andU.S. patents to Andreiko et al., U.S. Pat. Nos. 5,447,432, 5,431,562 and5,454,717. The system and method of Andreiko et al. is based onmathematical calculations of tooth finish position and desired idealarchform. The method of Andreiko et al. has not been widely adopted, andin fact has had little impact on the treatment of orthodontic patientssince it was first proposed in the early 1990s. There are a variety ofreasons for this, one of which is that the deterministic approachproposed by Andreiko et al. for calculating tooth finish positions doesnot take into account unpredictable events during the course oftreatment. Furthermore, the proposed methods of Andreiko et al.essentially remove the orthodontist from the picture in terms oftreatment planning, and attempt to replace his or her skill and judgmentin determining tooth finish positions by empirical calculations of toothfinish positions.

Typically, the wires used in orthodontic treatment today areoff-the-shelf products. If they need to be individualized by theorthodontist, the goal is to get along with as few modifications aspossible. Therefore, the brackets are designed in a manner that at theend of treatment, when teeth are aligned, the bracket slots are supposedto be located and oriented in a planar manner. This means that a wirethat would run passively through the slots, without applying any force,would be planar (flat). This treatment regime is known as “straightwire”. It dominates orthodontics worldwide. It is efficient for bothmanufacturers and the orthodontist. The customized orthodonticappliances proposed by Andreiko et al. call for a flat planar wire, butwith the curvature in a horizontal plane customized for the individualand dictated by the shape of the ideal desired archform for the patient.

The so-called straight wire approach that continues to be used inorthodontics today has some noteworthy disadvantages in terms of patientcomfort. The need to close the gap between the bracket bonding surfaceand the tooth surface with adhesive always leads to an increased overallthickness of the appliance. For brackets that are bonded labially, thisis acceptable, as labial tooth surfaces are very uniform for differentindividuals, and the gap to be closed is not significant. However,lingual (inner) surfaces of teeth show a much greater variation amongpatients. To achieve the goal to orient the bracket in a manner suchthat the slot is parallel to all other slots when treatment is finished,the thickness of adhesive that is necessary often is in the range of 1to 2 mm. It is obvious that every fraction of a mm added to appliancethickness significantly increases patient discomfort. Especially withlingual brackets (bracket bonded to the lingual surface of the teeth),articulation problems arise, and the tongue is severely irritated forseveral weeks after bonding. The tooth surfaces next to these adhesivepads are difficult to clean, thus serving as collecting point forbacteria and causing gingival inflammation. The further the archwire isaway from the tooth surface, the more difficult it is to achieve aprecise finishing position for each tooth. An error of only 10 degreesin torque (rotation around the wire axis) may well induce a verticalerror in tooth position of more than 1 mm.

Another significant disadvantage of thick brackets, especially whenbonding lingually, arises when the front teeth are severely crowded(which is often the cause for orthodontic treatment). Since the space ismore restricted at the lingual surface due to the curvature of the jaw,not all brackets may be bonded at one session. Rather, the orthodontisthas to wait until the crowding has decreased until all brackets may beplaced. Crowding also creates problems for labial brackets. Geometricalconsiderations dictate that this constriction problem becomes worse asthe thickness of the bracket/bracket bonding pad/adhesive combinationincreases.

Another problem in orthodontics is to determine the correct bracketposition. At the time of bonding, teeth may be oriented far away fromthe desired position. So the task to locate the brackets in a mannerthat a flat planar archwire drives teeth to the correct positionrequires a lot of experience and visual imagination. The result is thatat the end of treatment a lot of time is lost to perform necessaryadjustments to either bracket position or wire shape. This problem canbe solved by creating an ideal set-up, either virtually using 3D scandata of the dentition or physically by separating a dental model of thedentition into single teeth and setting up the teeth in a wax bed in anideal position. The brackets can then be placed at this ideal set-up atoptimal positions, in a manner that a flat wire running through thebracket slots would drive the teeth exactly into the ideal target. Thisagain may be done virtually in a computer or physically. After this isdone, the bracket position has to be transferred on a tooth-by-toothbasis into the maloccluded (initial) situation. Basing on thismaloccluded situation, a transfer tray enveloping the brackets can bemanufactured, which allows bonding the brackets exactly at the locationas defined at the set-up. Such as technique is taught generally inCohen, U.S. Pat. No. 3,738,005.

The published PCT patent application of OraMetrix, Inc., publication No.WO 01/80761, describes a wire-based approach to orthodontics based ongeneric brackets and a customized orthodontic archwire. The archwire canhave complex twists and bends, and as such is not necessarily a flatplanar wire. The entire contents of this document is incorporated byreference herein. This document also describes a scanning system forcreating 3D virtual models of a dentition and an interactive,computerized treatment planning system based on the models of thescanned dentition. As part of the treatment planning, virtual bracketsare placed on virtual teeth and the teeth moved to a desired position bya human operator exercising clinical judgment. The 3D virtual model ofthe dentition plus brackets in a malocclused condition is exported to arapid prototyping device for manufacture of physical model of thedentition plus brackets. A bracket placement tray is molded over themodel. Real brackets are placed into the transfer tray in the locationof where the virtual brackets were placed. Indirect bonding of thebrackets to the teeth occurs via the transfer tray. The system of WO01/80761 overcomes many of the problems inherent in the Andreiko et al.method.

During the course of treatment, brackets may come off, for instance ifthe patient bites on hard pieces of food. Obviously, the transfer trayused for initial bonding will not fit any more as teeth have moved.While it is possible to cut the tray (such as described in WO 01/80761)into pieces and use just the one section that is assigned to the bracketthat came off, to replace the bracket the reliability of this procedureis limited, as a small piece of elastic material is not adequate tosecurely position a bracket. It may therefore be required to create anew transfer tray adapted to the current tooth position using a costlylab process.

SUMMARY OF THE INVENTION

The customized orthodontic brackets described herein include severalindependent inventive features providing substantial improvements to theprior art. The greatest benefits will be achieved for lingualtreatments, but labial treatments will also benefit. While the followingsummary describes some of the highlights of various aspects of theinvention, the true scope of the invention is reflected in the appendedclaims.

Embodiments of the present invention provide custom orthodontic bracketsystem include a customized bracket having a precise bracket slot and anarchwire to be positioned in the bracket slot to thereby form a bracketslot-archwire interface. In particular, according to an embodiment ofthe present invention, the brackets have a bracket bonding pad orsurface for bonding the bracket to the tooth of the patient and abracket body having a precise bracket slot bracket slot having a bracketslot width and a bracket slot height positioned for receiving anarchwire having, for example, a flat, planar side (e.g., one side of awire having a rectangular, square, parallelogram or wedge-shapedcross-sectional shape) or an oval shape, positioned substantiallyadjacent the tooth surface to thereby reduce induced vertical error intooth positioning. According to an embodiment of the archwire, the firstcross-section of the archwire substantially matches the bracket slotheight and the second cross-section of the archwire substantiallymatches the bracket slot width.

According to an embodiment of the custom orthodontic bracket system, thebracket slots of the brackets are oriented in approximate parallelalignment relative to its respective bracket bonding pad in a mannersuch that, when the bracket or set of brackets are installed on theteeth of the patient and the archwire is inserted in the slots, thearchwire can be canted or inclined relative to the occlusal plane(analogous to a banked curve on a high speed racing track). In anembodiment in which the archwire has flat surfaces (rectangular,parallelogram, square, wedge shaped, etc), the flat planar side of thearchwire can be substantially parallel to the surface of the teeth atthe location of where the archwire is inserted into the slots, in acanted orientation relative to the occlusal plane. In an embodiment inwhich the archwire is of an oval configuration, the major axis of thecross-section of the wire can be oriented substantially parallel totooth surface and at a canted orientation relative to the occlusalplane.

Embodiments of the orthodontic bracket provide at least one brackethaving a bracket bonding surface for bonding the bracket to a tooth of apatient and a bracket slot to receive a customized archwire. The bracketslot can include opposed sidewalls with a distance between the sidewallssubstantially matching a first cross-section of the archwire to reducetorque rotation around the axis of the archwire when positioned thereinto thereby enhance end-of-treatment tooth positioning. This can include,for example, reducing induced vertical error. According to aconfiguration, the archwire also includes a second cross-sectionsubstantially perpendicular to the first cross-section. According tosuch configuration, the bracket slot can have a height substantiallyperpendicular to the distance between the sidewalls of the slotsubstantially matching the second cross-section of the archwire.

Embodiments of the archwire provide a customized archwire to bepositioned in a bracket slot of a bracket to thereby form a bracketslot-archwire interface. The archwire can include an axis and a firstcross-section defining a width of the archwire substantially matching atleast one bracket slot dimension to reduce torque rotation around theaxis of the archwire to thereby enhance end-of-treatment toothpositioning. The bracket can include a bracket bonding surface forbonding the bracket to a tooth of a patient and a bracket body having aprecise bracket slot to receive the archwire. The axis of the archwireis oriented at a preselected orientation to the occlusal plane of apatient when the archwire is positioned in the bracket slot.Correspondingly, the bracket slot can also include an axis oriented atthe preselected orientation to the occlusal plane of the patient and abracket slot width substantially matching the width of a portion of thearchwire adjacent the bracket slot to reduce torque rotation around anaxis of the archwire to thereby further enhance end-of-treatment toothpositioning and reduce overall treatment time.

For the front teeth, it is often desirable to come up with a homogeneousinclination to avoid abrupt changes in inclination (i.e., changes intorque) from slot to slot in order to receive a smooth progression ofthe wire. In a wire of rectangular or square cross-sectional shape, oneof the pairs of parallel opposite sides of the archwire is orientedsubstantially parallel to the tooth surface. Usually, this will be thepair of parallel sides that has the greater width or height. This aspectof the invention enables the overall thickness of brackets to besubstantially decreased as compared to prior art techniques, because itdoes not require a buildup of adhesive to make the slot lie in ahorizontal flat plane when the bracket is attached, as found in thestraight wire technique. The brackets and archwire design areparticularly well suited for use in lingual orthodontics.

This reduction in thickness of the bracket, bracket bonding pad andarchwire leads to several significant advantages as compared to priorart systems and satisfaction of a long-felt need in the art for a moresatisfactory lingual orthodontic system. These advantages includedecreased articulation problems, a pronounced decrease in tongueirritation, a decreased risk of bracket loss, increased positioningcontrol for finishing since the reduced distance between wire and toothresults in more accurate tooth movement to the desired finish position,increased patient comfort, and increased hygiene conditions.

One reason why the basic design of orthodontic wires remains one inwhich the wires have a flat, planar shape is the ease of industrialmanufacturing. To decrease the thickness of an orthodontic bracket, itis much preferable to run the wire parallel to the surface of eachindividual tooth as provided by this aspect of the invention. Thelingual surfaces of front teeth are significantly inclined relative to avertical axis for most patients. A wire that runs parallel from tooth totooth in accordance with this aspect of the invention has a “canted”shape in order to take advantage of the parallel nature of the bracketslots. Using standard mass-production procedures, such a wire could notbe fabricated, as every patient has a very individual tooth anatomy.Shaping a wire manually to provide the canted shape is extremelychallenging. Usage of modern materials for the archwire like shapememory alloys makes this task even more challenging or even impossibleby hand. However, in an embodiment of the present invention the requiredwire geometry is available in electronic format. This wire geometry canbe dictated by the three-dimensional location of the bracket slotsand/or the brackets, as placed on the teeth in the desired occlusion.This format can be exported to new wire bending robots that have beenrecently developed that are capable of bending wires in virtually anyshape (including canted shapes). For example, it is possible to exportdigital data reflecting wire geometry to flexible wire bendingproduction devices like the 6-axis-robot described in WO 01/80761, andhave the robot bend and twist wires of the canted configuration asdescribed herein. Thus, wires having the canted shape as dictated by thebracket invention are now able to be mass-produced. A wire-bending robotis also described in U.S. patent application Ser. No. 09/834,967, filedApr. 13, 2001, the content of which is also incorporated by referenceherein in its entirety.

Thus, in another and related aspect of the invention, a canted archwireis provided. The wire can be of any cross-sectional configuration thathas at least one flat planar surface, such as rectangular, or,alternatively, it could be oval in cross-section. The archwire is bentinto a configuration during manufacturing to have a shape, in a relaxed,as-manufactured condition, such that the flat planar surface of thearchwire (or the major axis of the cross-section of the wire in an ovalconfiguration) is canted relative to an occlusal plane over asubstantial arcuate extent. The canting of the archwire corresponds toportions of the archwire that are to be placed in brackets and used forstraightening two or more teeth. In an embodiment in which the wire isof rectangular or square cross-section, one of the first and secondpairs of parallel sides is oriented substantially parallel to toothsurfaces in the vicinity of where the archwire is to be received byarchwire receiving receptacles located on the two or more teeth.

In still another aspect, according to an embodiment of the presentinvention, a bracket is provided with an improved bracket bonding padthat makes the brackets essentially self-positioning. That is, it may beuniquely located and positioned on the teeth in the correct locationwith a positive fit without the use of a jig or other bracket placementmechanism, such as the tray as proposed by Cohen, U.S. Pat. No.3,738,005, or the jig of the Andreiko et al. patents. In particular, animprovement to a bracket having a bracket bonding pad is provided inwhich the bracket bonding pad has a tooth contacting surface ofthree-dimensional area extent conforming substantially exactly to thethree-dimensional shape of the tooth where the pad is bonded to thetooth.

In one possible embodiment, the three-dimensional area extent issufficiently large, and considerably larger than all bracket bondingpads proposed in the prior art, such that the bracket can be readily anduniquely placed by hand and located on the tooth in the correct locationdue to the substantial area extent corresponding to thethree-dimensional surface of the tooth. The bracket is able to be bondedin place on the tooth without the assistance of a bracket placement aidsuch as a jig. In another possible embodiment, the area extent covers acusp or a portion of a cusp to enable the bracket to uniquely be placedon the tooth.

In another aspect, a bracket is provided with a bracket bonding pad thatcomprises a thin shell in order to reduce the overall thickness of thebracket as much as possible. The pad includes a tooth-facing surfaceconforming to the surface of the tooth. In this embodiment, the bracketbonding pad has an opposite surface corresponding to the tooth-facingsurface which has a three-dimensional surface configuration which alsomatches the three-dimensional surface of the tooth.

In yet another aspect of the invention, according to an embodiment ofthe present invention, a method is provided for designing andmanufacturing a customized orthodontic bracket. The method includes thestep of storing a digital representation of the relevant portion of thepatient's dentition in a computer. This could be a digitalrepresentation of either the entire dentition, or alternatively only thesurfaces of the teeth upon which the brackets are to be bonded. Themethod continues with the steps of providing access to a library ofvirtual three-dimensional bracket bodies, such as for example storingthe library in the computer, and determining the shape and configurationof bracket bonding pads, with the bracket bonding pads having atooth-facing surface conforming substantially exactly to correspondingthree-dimensional surfaces of the teeth. The method continues with thestep of combining the bracket bodies from the library of bracket bodieswith the bracket bonding pads to thereby create a set of individual,customized orthodontic brackets. A file representing the customizedorthodontic brackets is exported from the computer to a manufacturingsystem for manufacturing the customized orthodontic brackets. The methodcontinues with the step of manufacturing the customized orthodonticbrackets, either using any of a variety of techniques known in the artsuch as milling, or one of the techniques described in detail hereinsuch as casting.

Still other improvements are provided for manufacturing customizedbrackets. In one aspect, a method is provided of manufacturing anorthodontic bracket having a bracket body having a slot and a bracketbonding pad, comprising the steps of determining the three-dimensionalshape of the orthodontic bracket and manufacturing the bracket frommaterials having at least two different hardnesses, a first relativelyhard material or materials forming the bracket body and a secondrelatively soft material or materials forming the bracket bonding pad.The strength of the material of the bracket is always a compromise.While the section forming the slot should be as robust as possible tomaintain the cross-section of the slot even when the bracket is exposedto high mechanical stress (e.g. by biting on hard objects), the sectionforming the pad should be softer to ease de-bonding after the treatmentis finished. If the pad is soft enough, it can literally be peeled offthe tooth surface, using an adequate tool. Depending on the type of themanufacturing process, it is possible to use different alloys to achievesuch a configuration. Using centrifugal casting, for example, first, acontrolled amount of a hard alloy can be used to form the section thatholds the slot, and afterwards a softer alloy is used to fill up theremainder of the bracket (or other way round). Controlling the amount ofmaterial needed to form a specific portion of the bracket is possible,since from the 3D models, the volume, and thus the tolerance, of eachcomponent of the bracket is precisely known. Other manufacturingtechniques can be used, such as a laser sintering process, in whichdifferent alloy powders are used for the different layers.

Advantageously, embodiments of the present invention provide acustomized orthodontic bracket system. According to an embodiment of thepresent invention a customized orthodontic bracket system is providedwhich includes a bracket having a bracket bonding pad for bonding thebracket to a tooth of a patient and a bracket body having an optimizedbracket slot adapted to receive an archwire. The system is adapted toform a precise bracket slot-archwire interface. Advantageously, themodular design can make it possible to define the bracket slot height tosubstantially match a cross-section of the archwire to reduce torquerotation around an axis of the archwire when positioned therein. Theoptimized bracket slot can also have a width adapted to match across-section of each archwire in a predetermined lot of archwires. Thebetter the bracket slot is adapted to the archwire thickness, the lessplay the archwire has in the bracket slot, and the more precise thetooth location will be at the end of treatment. Further, the bracketslot, and thus the archwire, when located in the mouth of the patient,can be positioned substantially adjacent the tooth surface to therebyreduce induced vertical error in tooth positioning. The bracket slot canalso be oriented substantially parallel to the surface of the tooth ofthe patient and canted relative to an occlusal plane to thereby reducebracket body thickness. Correspondingly, a major axis of the archwirecan also be canted relative to an occlusal plane to thereby runsubstantially parallel to the surface of the tooth and adjacent teeth toaid in reducing bracket body thickness. Further, advantageously, thebracket body can be selectively positioned on the bracket pad to preventcollisions with an opposing tooth during chewing.

According to an embodiment of the present invention, the bracket pad canbe shaped on both first and second sides substantially to conform to thethree-dimensional lingual surface of a tooth of the patient. The bracketpad can include a thin shaped body having a thickness equal to or lessthan 0.3 mm. The bracket pad can also be tapered between bracket padcenter and bracket pad perimeter edges. The bracket pad can be shaped onboth first and second sides substantially to conform to thethree-dimensional surface of the tooth. Such configurations can allowthe bracket to be hand positionable on the surface of the tooth withoutassistance of a bracket placement jig or tray. Also, the bracket pad canbe formed of a softer material than that of the bracket body to therebyenhance post-treatment de-bonding.

According to an embodiment of the present invention, a customorthodontic bracket system is provided which includes a customizedbracket having a bracket bonding pad for bonding the bracket to a toothof a patient and a bracket body having a custom bracket slot to receivean archwire, and a customized archwire adapted to be positioned in thebracket slot to thereby form a bracket slot-archwire interface. Thebracket slot can be oriented substantially parallel to a surface of thetooth of the patient. The bracket slot can have a bracket slot widthsubstantially matching a cross-section of the archwire to reduce torquerotation around an axis of the archwire to thereby enhanceend-of-treatment tooth positioning. The bracket slot can also have abracket slot height substantially matching the height of the archwireadjacent the bracket slot to reduce torque rotation around an axis ofthe archwire to thereby enhance end-of-treatment tooth positioning andreduce overall treatment time. The archwire, when positioned in thebracket slot of each of a plurality of brackets, is advantageouslysubstantially adjacent each tooth surface to thereby reduce inducedvertical error in tooth positioning.

According to an embodiment of the present invention, a customorthodontic bracket system is provided which includes a customizedbracket having a bracket body and a bracket bonding pad for bonding thebracket to a tooth of a patient, and includes a customized archwire. Thebracket body can have a custom bracket slot adapted to receive thearchwire and can be oriented substantially parallel to a surface of thetooth of the patient to thereby reduce bracket body thickness and can bepositioned substantially adjacent the tooth surface to thereby reduceinduced vertical error in tooth positioning. The customized archwire isadapted to be positioned in the bracket slot to thereby form a bracketslot-archwire interface. The archwire can also be canted relative to anocclusal plane when positioned in the bracket slot to run substantiallyparallel to the surface of the tooth. A first cross-section of thearchwire can substantially match the bracket slot height and a secondcross-section of the archwire can substantially match the bracket slotwidth to reduce torque rotation around an axis of the archwire tothereby enhance end-of-treatment tooth positioning.

These and still other principles of the various inventions set forthherein will be discussed in greater detail in conjunction with theappended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Presently preferred embodiments of the invention are described below inconjunction with the appended drawing figures, where like referencenumerals refer to like elements in the various views, and wherein:

FIG. 1 is a perspective view of a canted archwire in accordance with oneaspect of the invention.

FIG. 2 is an illustration, partially in cross-section, showing a set ofteeth, associated brackets and the archwire of FIG. 1.

FIG. 2A is a cross-section of an archwire with an oval cross-sectionthat could be used in one possible implementation of this invention.

FIG. 2B is a cross-section of the archwire of FIG. 2A placed in abracket slot with the slot of the bracket oriented substantiallyparallel to the tooth surface, showing the archwire major axis orientedin a canted configuration with respect to the occlusal plane.

FIG. 3A is a cross section of a tooth with a bracket bonding pad andslot oriented substantially parallel to the tooth surface in accordancewith one aspect of a preferred embodiment of the invention.

FIG. 3B is a cross-section of the same tooth shown in FIG. 3A but with aprior art arrangement of a standard Ormco lingual bracket, showing thebracket slot orientation for a horizontal planar archwire that is notcanted as shown in FIG. 3A.

FIG. 4 is a perspective view of computer model of two teeth with abracket bonding pad in accordance with one aspect of the inventionperfectly adapted to the tooth surface and covering a substantial areaextent of the tooth surface so as to render the bracket manuallyplaceable by the orthodontist in the correct location on the toothwithout the use of a jig or other bracket placement device.

FIG. 5 is a view of bite plane devices that may be incorporated onto abonding pad and bonded on the tooth in order to prevent the upper andlower jaws from closing completely.

FIGS. 6A, 6B and 6C are standard bracket body shapes that may be used inthe design of customized orthodontic brackets. These and other types ofbracket bodies are stored as a library of virtual bracket body objectsin a computer and used to design customized orthodontic brackets asdescribed in further detail.

FIG. 7 is a top view of three lower front teeth, showing, in a somewhatsimplified manner, how the location of the bracket body on the bracketbonding pad can be adapted to take into consideration the crowdingcondition of the teeth. The adaptation shown in FIG. 7 is simulated on acomputer workstation implementing a bracket design program and allowsthe user to position the bracket body on the bracket bonding pad in anyarbitrary location in order to optimize the placement of the bracketbody for the individual patient. The ability to place the bracket bodyoff-set from the center of the pad can be a benefit for labial brackets,e.g., shifting the bracket body in the gingival direction for a lowersecond bicuspid similar to that provided by the Ormco Mini Diamond™bracket with gingival offset. This provides a larger bonding areawithout moving the slot too far to the occlusal portion of the tooth.

FIG. 8 is an illustration of an Ormco Spirit™ MB ceramic bracket with aninlay for the slot of the bracket.

FIG. 9A is an illustration of a virtual tooth displayed on a computerworkstation implementing the bracket design features of the presentinvention, with the user marking the boundary of a bracket bonding padon the surface of the tooth by placing points on the surface of thetooth. FIG. 9B is an illustration of a curved boundary for the bracketbonding pad, created by joining the points in FIG. 9A with by lines thatfollow the contour of the tooth surface.

FIG. 10 is an illustration of a set of virtual teeth displayed on acomputer workstation implementing the bracket design features of thepresent invention, showing the pad boundaries that the user has createdfor a set of teeth. Note that the surface of the teeth covered by thebracket bonding pads may comprise a substantial area extent of thelingual surfaces of the teeth, in this instance approximately 60-75percent of the lingual surface of the teeth, to assist the user incorrectly placing the bracket on the tooth. The area coverage depends onthe curvature of the tooth surface, with relatively flat tooth surfacesrequiring greater bonding pad area coverage in order for the bracket tobe able to be correctly placed without a jig. Where the bracket bondingpad covers part of a cusp of a tooth, the area coverage can be reduced.

FIG. 11 is an illustration of the tooth surface that is to be covered bythe bracket bonding pads. These tooth surfaces are “cut” or separatedfrom the tooth models by performing a separating operation on theworkstation, rendering these objects independent three-dimensionalsurfaces of zero thickness.

FIG. 12 is a view of a set of teeth, partially in cross-section, showinga bracket bonding pad overlying a tooth surface and a bracket bodyplaced on the bracket bonding pad, in an interim step in the performanceof a method of designing a customized bracket. The portion of thebracket body projecting into the tooth is eventually removed from thebracket, as shown in FIG. 21.

FIGS. 13A and 13B are perspective views of two representative bracketbodies in which the surfaces thereof are shaped according to the toothsurface, wherein the slots are oriented generally substantially parallelto the surface of the tooth adjacent to where such bracket bodies arebonded to the teeth.

FIG. 14 is perspective view of a digital representation of a set oftooth objects and brackets objects designed in accordance with apreferred embodiment of the invention.

FIG. 15A is an illustration of a prior art lingual bracket arrangement.

FIG. 15B is an illustration of the same teeth but with customizedbrackets in accordance with the bracket design features of thisinvention. A comparison of FIGS. 15A and 15B shows the pronounceddecrease in bracket thickness in FIG. 15B.

FIG. 16 shows the combination of a virtual bracket body and virtualbracket bonding pad during an intermediate step in the design of acustomized orthodontic bracket, in which the pad and bracket body aretwo independent three-dimensional virtual objects which can be movedrelative to each other.

FIG. 17 shows the screen of a computer workstation implementing thebracket design features described herein, in which the user is unitingthe pad and bracket body of FIG. 16 into a single virtual object.

FIGS. 18A and 18B are two views of the pad and bracket body combined asa single virtual object

FIG. 19 shows the pad and bracket body of FIGS. 18A and 18B placed on avirtual tooth.

FIG. 20 shows the screen of a computer workstation performing asubtraction process to subtract the tooth object represented in red onthe workstation from the bracket bonding pad/bracket body objectrendered in green on the workstation. This step is needed to remove theportion of the bracket body that would otherwise project inside thetooth.

FIGS. 21A and 21B are two views of the bracket pad/bracket body objectafter the subtraction operation of FIG. 20 has been performed. Bycomparing FIG. 17 with FIG. 21B, it will be seen that the portion of thebracket body that would have otherwise projected within the tooth hasbeen deleted from the bracket pad/bracket body object.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings in which embodiments of theinvention are shown. This invention may, however, be embodied in manydifferent forms and should not be construed as limited to theillustrated embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will be thorough and complete, and willfully convey the scope of the invention to those skilled in the art.Like numbers refer to like elements throughout.

Bracket Slot Parallel to Tooth Surfaces and Canted Archwire

As noted earlier, in the straight wire approach to orthodonticspracticed today, the basic design of orthodontic wires in the prior artis a flat, planar shape. All the slots of the brackets, when the teethare moved to the desired occlusion, lie in a plane. Accordingly, thearchwire itself, which is of rectangular cross-section, has a flat,planar configuration. This is also the case for wires to be used withthe CONSEAL™ brackets mentioned previously. While the cross-section ofthe wire is oriented in a vertical manner (the longer side of the wireis vertical), the archwire still forms a plane that is substantiallyparallel to the occlusal plane and the orientation of the cross-sectionis maintained along the wire. The primary reason for this phenomenon isthe ease of industrial manufacturing of archwires of flat planarconfiguration. In a first aspect of the invention, we propose asignificant departure from flat, planar archwires.

In particular, we have realized that to decrease the thickness of anorthodontic bracket, it is much more preferable to construct the slotsof the brackets, and manufacture the archwire, such that the archwireruns essentially parallel to the surface of each individual tooth. Inone aspect of the invention, the bracket slots are oriented in a mannersuch that the wire runs substantially parallel to each tooth surface.What we mean by this is that when a wire, with at least one flat planarsurface, is inserted into the bracket slots, the flat planar surface ofthe archwire is canted or tilted at an oblique angle relative to theocclusal plane. For example, with a wire of rectangular or squarecross-sectional shape, one of the pairs of surfaces of the wire isoriented parallel to the tooth surface in a manner inclined relative tothe occlusal plane. Similarly, if the wire has an oval cross-section,the major axis of the wire (see FIG. 2B) is oriented substantiallyparallel to the tooth surface and is inclined at an oblique anglerelative to the occlusal plane.

The lingual surfaces of front teeth are significantly inclined. A wirethat runs parallel from tooth to tooth particularly in the front teethwould have to have a “canted” shape (analogous to a banked curve on ahigh speed racing track) relative to the occlusal plane. Using standardmass-production procedures, such a wire could not be fabricated, asevery patient has a unique tooth anatomy. Shaping a wire manually isextremely challenging. Usage of preferable materials like shape memoryalloy makes this task even more challenging or literally impossible.However, in a preferred embodiment of this invention, the required wiregeometry is available in electronic format. It is possible to transporta file representing this wire geometry to a flexible production devicelike a 6-axis wire bending robot described in WO 01/80761 to bend andtwist wires of such a shape.

FIG. 1 is a perspective view of an archwire 10 with flat sides that is“canted” as provided in this first aspect of the invention. The archwirein the illustrated embodiment is of rectangular cross-section and hastwo pairs of parallel sides. One of the pairs of parallel sides 12 is ofgreater height (perpendicular to the axis of the wire) than the other,at least for non-square cross-section wires, and in this embodiment thepair of sides 12 which have the greater height is oriented generallyparallel to the tooth surfaces. This can be seen more readily in FIG. 2,which shows the archwire received by three brackets 14 on three of thefront teeth 16. The brackets 14 consist of a bracket bonding pad 18 anda bracket body 20 that includes an archwire-receiving slot 22. The slotsof the brackets 14 are oriented in approximate parallel alignmentrelative to its respective bracket bonding pad 18 and associated toothsurface. The arrangement of the bracket slots 22 is in a manner suchthat, when the brackets 14 are installed on the teeth 16 of the patientand the archwire 10 is inserted in the slots 22, the archwire 10 iscanted or inclined relative to an occlusal plane. One of the pairs ofparallel opposite sides of the archwire (12 in FIGS. 1 and 2) isoriented substantially parallel to the tooth surface. This aspect of theinvention enables the overall thickness of brackets to be substantiallydecreased as compared to prior art techniques, making the brackets andarchwire design particularly well suited for use in lingualorthodontics. The overall thickness of the bracket is also reduced byproviding the bracket bonding pad with tooth facing surface and oppositesurfaces which conform to the three-dimensional surface of the tooth.Thus, the pad can be constructed as a thin shell (e.g., 0.3 mm inthickness) matching the tooth anatomy.

It is important to note that the canted archwire 10 shown in FIG. 1 isshown “as-manufactured.” In other words, the wire has the shape shown inFIG. 1 when the teeth are moved to the finish position and no furtherforces are imparted onto the teeth. When the wire of FIG. 1 is installedon the teeth in the malocclused condition, the wire will have some othershape, due to the malocclusion, but since the brackets are bonded to theteeth and the bracket slots are oriented generally parallel to the toothsurface, the archwire 10 will still be oriented such that the sides 12of the archwire are parallel to the tooth surface, thereby providingnumerous clinical benefits.

FIG. 2A is a cross-sectional view of an oval archwire 10. The archwirecross-section has an oval configuration with a long or major axis 11 anda minor axis 13. As shown in FIG. 2B, the bracket slot 22 is orientatedbasically parallel to the tooth 16 surface and the wire 10 is installedin the bracket slot such that the major axis 11 is oriented in a cantedor inclined position relative to the occlusal plane 15.

FIGS. 3A and 3B illustrate the advantage of the bracket design and acanted wire: the overall thickness of the bracket can be greatlyreduced. FIG. 3A shows the design of a bracket in which the slot 22 isoriented parallel to the tooth surface 16A. FIG. 3B shows a prior artbracket in which the slot 22 is oriented at a substantial angle to thetooth surface at 16A. The bracket slot is parallel to the occlusalplane. In the case of anterior teeth, this results in an inclinationbetween the lingual tooth surface and the bracket slot of approximately45 degrees. It should be noted here that when we speak of theorientation of the slot, we are referring to the direction of the slotfrom the opening of the slot 22A to the base of the slot 22B, and notthe transverse direction parallel to the axis of the archwire. Thus, theslot in FIG. 3A is oriented parallel to the tooth surface 16A in FIG.3A. The same orientation is found for all the brackets in FIG. 2. Incontrast, the slot in FIG. 3B is oriented at roughly a 45 degree angleto the tooth surface 16A. The slot in the prior art arrangement of FIG.3B is such that the wire has a flat planar surface that is perpendicularto the occlusal plane, and not canted at an oblique angle as is the casein FIG. 3A and FIG. 2B.

The bracket bonding pad 18 illustrated in FIGS. 2 and 3A conformsexactly to the three-dimensional surface of the tooth and consists of athin shell. These aspects of the bracket design are described in furtherdetail below.

The reduction in thickness provided by the bracket design of FIGS. 2, 2Band 3A leads to a number of significant improvements as compared to theprior art design shown in FIG. 3B, particularly for lingualorthodontics:

-   -   decreased articulation problems;    -   decreased tongue irritation;    -   decreased risk of bracket loss (the flatter the bracket is, the        shorter the moment arm is when a patient bites onto the bracket,        and the smaller the stress at the adhesive connection);    -   increased positioning control for finishing (the smaller the        distance between wire and tooth is, the better the tooth        “follows” the wire);    -   increased patient comfort; and    -   increased hygiene conditions.

The orientation of the archwire 10 at the molars may be vertical, asshown in FIG. 1, which results in minimal overall thickness at themolars, or alternatively it could be horizontal. The horizontalorientation would add more thickness (for instance 0.025 inches per sideinstead of 0.017 inches for a typical wire cross section of 17×25), butthe addition is so small that this would certainly be acceptable, ifmanufacturing or clinical considerations would call for such anorientation. Since a horizontal slot orientation is acceptable formolars and premolars, it would also make sense to mix conventionalbrackets with brackets according to this invention. For example, thepremolars and molar brackets could be conventional brackets, while a setof brackets according to this invention would be supplied for theanterior and canine teeth.

Thus, in one aspect of the invention we have described a bracket, and aset of brackets 14, having slots 22 in which the slots 22 of each of thebrackets 14 are oriented in approximate parallel alignment relative toits respective bracket bonding pad 18 in a manner such that, when theset of brackets are installed on the teeth 16 of the patient and thearchwire 10 is inserted in the slots, the archwire 10 is canted relativeto an occlusal plane to conform to the surface of the teeth at thelocation of where the archwire 10 is inserted into the slots 22 wherebythe overall thickness of the brackets may be decreased.

As shown in FIGS. 2 and 3, the pair 12 of sides of the archwire 10 areoriented substantially parallel to the bracket bonding pad 18 in theregion 16A when the archwire 10 is inserted into the slots 22. As shownin FIGS. 2 and 3A, in a preferred embodiment each bracket bonding padhas a three-dimensional tooth facing surface 24 that has a shape toconform exactly to the three-dimensional surface of its respectivetooth.

The invention is applicable to both labial brackets and lingualbrackets. The brackets in one possible embodiment are essentiallyself-positioning, as described in more detail below, in that they can bepositioned on the tooth in the correct location without the assistanceof a bracket placement jig or tray. In the embodiment of FIG. 2, thebrackets 14 are lingual brackets and the bracket bonding pad for each ofbrackets covers a sufficient portion of the lingual surface of therespective tooth so as to be uniquely positioned on the teeth by hand.Note also in FIG. 3A that the bracket bonding pad has a second oppositesurface 26 having a three-dimensional shape corresponding to thethree-dimensional tooth-facing surface 24 to thereby further decreasethe thickness of the bracket.

In one possible embodiment the set of brackets according to thisinvention may comprise all the brackets for treatment of an arch of thepatient. On the other hand, the set of brackets may comprise less thanall the brackets for treatment of an arch of the patient and comprise atleast one bracket, since the brackets can be mixed with conventionalbrackets. A set of brackets for placement on the lingual surface of thefront teeth of the patient is one representative embodiment. Further,the set of brackets may comprise one subset of brackets for placement onthe lower arch and a second subset of brackets for placement on theupper arch.

As noted above, in one possible embodiment the opposite surface of thetooth-facing surface matches the three-dimensional surface of the tooth.The thickness of the bonding pad could be the same across the bondingpad (e.g., 0.3 mm), or alternatively it could vary from say 0.1 mm atthe edge of the bonding pad to 0.3 mm in the center. This latterembodiment would provide the required stability on the one hand, and onthe other hand promote a peeling off of the pad from the tooth whentreatment is completed. Further, the thinner the pad the greater thepatient comfort. Presently, casting brackets with a thickness below 0.3mm is quite challenging, but other manufacturing technologies such asmilling or laser sintering could be used instead for manufacturing thepads.

Further design and manufacturing considerations for the brackets ofFIGS. 2 and 3A are discussed in detail later on this document.

Self-positioning Brackets

The “footprint” of the surface 24 of the bracket 14 that is bonded tothe tooth (“pad”) is a compromise if non-customized pads are used. Thesmaller it is, naturally the discrepancy between the pad surface and thetooth surface is smaller, and the need to close significant gaps isreduced. On the other hand, the larger it is, the more stable theadhesive joint is, and the smaller the risk of a bracket coming offduring the course of treatment.

In another aspect of the invention, we overcome this compromise byshaping the bracket bonding pads 18 (FIGS. 2 and 3A) exactly accordingto the associated tooth. The shape of the pad's tooth-facing surface 24is formed as a negative of the tooth surface. This ensures that noconflicts between tooth surface and bracket surface can arise, resultingin the possibility to design each bracket as flat as possible andtherefore getting the wire as close to the tooth surface as possible. Avery welcome result of this approach is that the bonding surface can bemade very large for teeth that show no prominent curvature on thebonding surface, or where the bonding surface can follow the curvatureof the cusps. This improves adhesive strength, and by covering asubstantial amount of tooth anatomy, the position of the bracket iscompletely defined by the bracket itself. Even without performingindirect bonding, each bracket is placed exactly at the desiredposition. If a bracket should still come off, it can easily berepositioned without additional efforts. Because of the bracket bondingpad either covering a substantial area extent of the surface of thetooth or being perfectly adapted to prominent curvatures like cusps, itcan be positioned uniquely in the correct location by hand without anyjigs or other bracket placement devices. If a bracket comes off duringthe course of treatment, manual repositioning using the positive fit ishighly desirable and indeed possible with these brackets. However, forinitial bonding, the use of a tray to simultaneously position multiplebrackets may be employed.

The substantial area extent or coverage of the bracket bonding paddepends on the curvature of the tooth surface. In teeth that are ratherflat, like the lower anteriors, the area extent may need to be as largeas 50 percent or more of the tooth surface for lingual brackets andpreferably 70 percent or more for labial brackets. For lingual brackets,this area coverage of the bracket boding pad 18 can be 60 to 75 percentor more. The bracket bonding pads may cover, at least in part, portionsof the cusps of the teeth, preferably where such cusps do not makecontact with opposing teeth during occlusion or chewing. Where thebracket bonding pad covers the cusp, the manual placement of the bracketand close and unique fit of the bracket to the tooth is furtherpromoted.

FIG. 4 shows an example of lingual brackets 14 in which the bracketbonding pad 18 covers more than 50 percent of the tooth. The bracketbonding pad has a three-dimensional tooth-facing surface 24 (FIG. 3A,not shown in FIG. 4) that is a negative of the surface of the tooth anda second surface 26 which also has the same three-dimensional toothsurface. The manner in which the surfaces 24 and 26 are designed isdescribed in more detail below. Note that the bracket slots need not beparallel to the teeth in this embodiment. Also note that the bracket pad18 for tooth 16B covers part of the cusp in region 30.

Bracket Design

Brackets according to this appliance system have to be fabricatedindividually for every patient. Doing this in a lab process would betime consuming and expensive. Designing the bracket slots in the optimalorientation is also challenging. The invention solves this problem bydesigning the brackets, including the pad geometry in a preferredembodiment, with the help of a computer using virtual three dimensionalbracket bonding pads, virtual bracket bodies, and virtual auxiliarydevices for brackets such as hooks.

In a preferred embodiment, the bracket design is performed in aworkstation that stores a three-dimensional virtual model of thepatient's dentition and preferably treatment planning software formoving the teeth in the virtual model to desired finish positions. Suchcomputers are known in the art. See, e.g., WO 01/80761 and Chisti etal., U.S. Pat. Nos. 6,227,850 and 6,217,325, incorporated by referenceherein. The design of the brackets in accordance with this invention canbe done by a user at an orthodontic clinic, or could be performed at aremotely located manufacturing site.

The pad 18 geometry can be derived directly from digital representationsof the patient's teeth so as to produce a bracket bonding pad thatconforms substantially exactly to the shape of the surface of the teeth.To achieve this, the shape and size of the bracket pad for each tooth isdetermined. This may be done manually by using a computer program thatallows indicating the desired areas on each tooth model, for instance bydrawing virtual lines onto the tooth models or coloring the respectiveareas. A 3D graphics software program like Magics™ that is widely usedto manipulate 3D models that are defined as a set of interconnectedtriangles (STL-format), allows marking triangles by simply clicking atthem with the mouse.

Another option is to use a software algorithm that automatically orsemi-automatically calculates an appropriate bracket bonding pad area byanalyzing the curvature of the tooth surface and determining a surfacethat is large enough to cover substantial curvature features to allowfor reliable manual positioning of the bracket onto the tooth surface.Such an algorithm could for instance start with a pre-defined pad size.The tooth surface covered by that pad size would form a virtual “knoll”having at least one raised portion relative to surrounding toothanatomy, as a completely flat tooth surface would not lend itself tounique positioning of a bracket. The volume of the knoll could becalculated provided that the edges of the pad are joined by a continuoussurface in any convenient manner. The less curvature the tooth surfacepresents, the flatter the knoll and the smaller its volume would be. Ifthe volume of the “knoll” does not exceed a pre-defined value, the padwould automatically be enlarged by a pre-defined value, with the ideathat the larger volume would be more likely to include adequate raisedtooth features. Again, the volume would be calculated. This loop wouldbe continued until a minimum volume value would be achieved for eachpad. Obviously, this is just an exemplary approach for such an automatedalgorithm. Others could be readily developed from the principles taughtherein.

An implementation of the bracket pad shape design process is describedin further detail below.

Once the pad 18 areas are defined, the shape of this portion of thetooth defines exactly the required shape of tooth-facing portion of thebracket pad. There are several options how to shape the outside portionof the pad. In order to receive a thin pad, the best method is to createthe normal vector of each surface element (for instance, a triangle)describing the tooth-facing surface of the pad, and to “shift” eachsurface element in the direction of the normal vector using apre-defined offset value corresponding to the desired thickness of thebracket bonding pad. In this way a thin shell is created, the outside ofthe shell having the same contour (albeit shifted) as the tooth-facingside. Alternatively, the thickness of the bracket can vary over thesurface of the pad with the pad thickness the least at the edges (e.g.,0.1 mm) and greatest (e.g., 0.3 mm) in the center.

The other part of the bracket, the body 20, containing the slot 22 andfurther features that allow fastening the wire into the slot(“ligating”), may exist as a predefined virtual model in the computer,as the body does not need to be patient specific. Typically, a libraryof bracket bodies will be created and stored in the computer. FIGS.6A-6C show perspective views of three-dimensional virtual bracket bodiesthat are stored in a library of bracket bodies 20 and used for purposesof design of a custom bracket for an individual patient. Alternatively,and equivalently, the library of bracket bodies could be storedelsewhere and accessed remotely. It would be possible to hold a varietyof different bodies for different malocclusions and treatment approaches(severe/moderate crowding, extraction/non-extraction etc.). It is alsopossible to add virtual auxiliary features to the brackets from alibrary of such features. If, for instance, elastics are required toapply forces along the arch (space closure etc.), hooks may be added. Ifa patient has a significant overbite and it is desired to preventhim/her from completely closing the jaw, so-called bite planes can beintegrated into the bracket. To illustrate this, FIG. 5 shows appliancescalled bite turbos 32. These appliances 32 are not brackets, but onlyserve the purpose of providing such a bite plane in order to preventboth jaws from closing completely.

It would even be possible to modify models of bracket bodies accordingto the requests of an orthodontist. Another advantage is thatexperiences that are made on certain treatments can almostinstantaneously be transformed into the design of the bracket bodies inthe library.

After the shape of the bracket bonding pad (including the tooth-facingsurface 24 and the opposite surface 26) has been defined, and the userhas selected the bracket body 20 that they wish to use for the givenbracket bonding pad, the next step is to combine the bracket body 20with the pad 22. Common Computer Aided Design (CAD) programs haveseveral capabilities to design freeform shapes and to connect existingshapes to each other. One specific method is described in detail belowin the Exemplary Embodiment section. Preferably, the user specifies howthe bracket body is to be united with the bracket bonding pad to achievea desired configuration for the customized bracket.

Since the exact spatial relation of bracket body and pad can be randomlydefined using state of the art 3D graphics software, it is possible todeal for instance with crowded front teeth. The bracket body can beshifted slightly to the left or to the right to avoid conflicts withadjacent teeth and/or brackets, either at the start of treatment orduring the course of tooth movement during treatment. This feature isshown in FIG. 7. Note that the position of the bracket body 20A for theleft tooth 16A and the bracket body 20B for the right tooth 16C aremoved toward one side of the bracket bonding pad 18, so as to avoidcollisions between the bracket and the teeth at the start of treatment.Similarly, the bracket body may be moved up or down to avoid a collisionwith the teeth on the opposing jaw. Alternatively, the user could simplyenlarge the pad surface.

As yet another possible embodiment, we contemplate providing the abilityof a user to design, with the aid of a computer, a virtual bracketcustomized for a particular patient. The user is provided with a librarycontaining a plurality of available virtual bracket bonding pads,virtual bracket bodies and optionally virtual auxiliary features. Thepad's geometrical shape could be pre-defined (that is, of a givenconfiguration) or could be defined in three dimensions to fit thethree-dimensional surface of the patient's teeth exactly as described indetail herein. For example, it would be possible for an orthodontist toorder a given pad (for example, pad number 0023 of a list of availablepads, with pad 0023 having a predetermined shape), united with aparticular bracket body (bracket body number 0011 selected from a listof available bracket body styles), and equipped with hook number 002 forthe upper left canine The user could specify how they wish to unite thebracket bonding pad to the bracket body (such as set forth herein), orthey could leave that to the manufacturer. In one possible embodiment,the user specifies the bracket bonding bad, bracket body and auxiliaryfeatures, views these components as virtual objects on a workstation orcomputer, and unites the objects together them to arrive at a uniquecustomized bracket. They then export data representing the bracket to amanufacturing system (such as rapid prototyping system) for directmanufacture of the bracket, or manufacture of a template or model thatis used for manufacture of the bracket using a casting process.

Bracket Manufacturing

Once the pad and bracket body have been joined into one 3D object, datarepresenting this object can be exported, for instance in STL format, toallow for direct manufacturing using “rapid prototyping” devices. Thereare already a wide variety of appropriate rapid prototyping techniquesthat are well known in the art. They include stereolithography apparatus(“SLA”), laminated object manufacturing, selective laser sintering,fused deposition modeling, solid ground curing, and 3-D ink jetprinting. Persons skilled in the art are familiar with these techniques.

In one possible technique, it is possible to use a so-called “waxprinter” to fabricate wax models of the brackets. These wax models willthen be used as a core in a casting process. They are embedded in cementand then melted. The brackets would be cast in gold or anotherapplicable alloy as known to those skilled in the art. It would also bepossible to create SLA models and use these as cores in a mold. Otherprocesses, like high-speed milling, could also be used to directly millthe brackets. Processes like laser sintering, where a powdery substanceis hardened by a digitally controlled laser beam, are applicable. Thepowdery substance could be plastic, thus creating cores for a mold, orit could be metal, thus directly fabricating the brackets.

Most rapid prototyping devices shape the objects in layers. Thistypically causes steps, when a surface is to be modeled is unparallel tothe layers. Depending on the thickness of the layers, these steps mayhardly be noticeable. However, the surfaces forming the bracket slot 22should be smooth. One option is to accept steps during the rapidprototyping manufacturing and to mechanically refinish the slots as alast manufacturing step. A better option is to avoid steps by orientingthe 3D models inside the rapid prototyping device in a manner that theslot is parallel to the layers. In this case, the desired height of theslot must correspond to the layer thickness. In other words, the slotheight must be an integer multiple of the layer thickness.

Another option to receive a smooth slot surface is to manufacture theslot larger than the target size and to insert a machined or moldedU-shaped inlay into the slot, the inlay thus forming the slot. This isfor instance often done at ceramic brackets to reduce friction betweenwire and slot. This is shown in FIG. 8, in which a U-shaped inlay 40 isplaced into the slot 22.

The strength of the material of the bracket 14 is always a compromise.While the section forming the slot 22 should be as robust as possible tomaintain the cross-section of the slot even when the bracket is exposedto high mechanical stress (e.g., by biting on hard objects), the sectionforming the pad 18 should be softer to ease de-bonding after thetreatment is finished. If the pad is soft enough, it can literally bepeeled off the tooth surface, using an adequate tool. Depending on thetype of the manufacturing process, it is possible to use differentalloys to achieve such a configuration. Using centrifugal casting,first, a controlled amount of a hard alloy can be used to form thesection that holds the slot, and afterwards a softer alloy is used tofill up the remainder of the bracket (or other way round). Controllingthe amount of material needed to form a specific portion of the bracketis possible, since from the 3D models of the brackets, the volume ofeach bracket section is precisely known. If a laser sintering process isused, different alloy powders may be used for the different layers,assuming that the design of the device allows such a procedure.

The modular design generally makes it possible to define the slot heightto exactly match the wire cross section. The better the slot is adaptedto the wire thickness, the less play the wire has in the slot, and themore precise the tooth location will be at the end of treatment. Itwould be possible to adapt the slot size of the brackets to a certainlot of wires to be inserted.

The better defined the system bracket/wire is, the less problems willarise during finishing, and the less time will be consumed to deal withsuch problems. This results in decreased overall treatment time.

Exemplary Embodiment

The process described below is a process that has already beensuccessfully tested. From the comments in the section above, it isobvious that many variations are possible. The reader is directed toFIGS. 2, 3A and 9A-15 in the following discussion. The followingdiscussion is made by way of disclosure of the inventor's best modeknown for practicing the invention and is not intended to be limiting interms of the scope of the invention.

First, a digital three-dimensional representation of the patient'sdentition is created or otherwise obtained. One option would be togenerate a representation of the malocclusion from a scanning of themalocclusion (either in-vivo or from scanning a model), in which casethe digital models of the teeth derived from the digital representationof the dentition would be re-arranged to a desired finishing positionwith a computer treatment planning program. This process is described atlength in WO 01/80761. Another option is to manually create such afinishing position, using a lab process where plaster models are cutinto single tooth models, and these tooth models are re-arranged byplacing them in a wax bed (“set-up”). A digital representation of theideal finishing position is then created by scanning this set-up usingan industrial laser scanner. This process is also known in the art, seefor example the Chisti et al. patents cited earlier.

Once the digital representation of the ideal finishing tooth positionhas been created, the size and shape of the bracket pad is determinedfor every tooth. This step, and subsequent steps, have been performedusing an off-the-shelf 3D graphics software program known as Magics™,developed by Materialise. Other software programs are of coursepossible.

For each tooth, the area to be covered by the pad 18 is selected byusing the cutting functionality. This is shown in FIGS. 9A and 9B. Byclicking at multiple points 50 on the surface of the tooth forming thedesired boundary of the bracket bonding pad, this portion of the toothmodel is selected for forming the surface at which the bracket bondingpad will be bonded to the tooth. The points 50 are connected by lines 52automatically. The resulting 3-D polygon is smoothed and the surfaceenclosed by a line. This surface is turned into an independent surfaceobject in the computer. FIG. 10 shows the process performed for a set offour teeth. The surfaces 54 of the tooth are turned into independentobjects as shown in FIG. 11, and consisting of a three-dimensional shellof zero thickness. These surfaces 54 serve as the tooth-facing surfacesof the bracket bonding pad.

Next, the function “Offset Part” in the Magics software is used. Option“Create Thickness” is activated, that uses the normal vectors of thetriangles forming the surface 54 to offset the shell 54 and in this wayto create a second shell which forms the opposite surface 26 of thebracket bonding pad 18, which is then combined to one continuous surfaceby closing the gap around the outer edges of the shell. In this way, thethree-dimensional shape of the pad 18 is defined. Today's castingtechnologies will require the pad to have a thickness of typically 0.3mm.

Next, from the library of virtual bracket body models, the appropriatemodel of a bracket body is selected for the respective tooth. Typically,one would have different bodies for molars, premolars and front teeth.FIG. 12 shows the placement of a bracket body 20 from the library on abracket bonding pad 18 at this interim step in the process.

The portion of each bracket body 20, that needs to be merged with thepad 18, is designed to be much longer that needed, so it will stick outon the tooth-facing side of the pad when oriented properly with respectto the tooth. This is the situation shown in FIG. 12. Of course, this isundesirable and the portion projecting inwards from the bracket bondingpad needs to be eliminated.

To make a bracket that is as thin as possible (e.g., for lingualtreatments) the goal is obviously to position the slot 22 as close tothe pad 18 as possible without creating interference between the paditself and the slot, or the wire when it runs through the slot.

To remove the portion of the body 20 that is sticking out of the padtowards the interior of the tooth, the original tooth models arere-loaded. The Magics™ software provides “Boolean” operations thatinclude unite functions and subtraction functions. Using thesefunctions, as described below in conjunction with FIGS. 16-21, all partsof the bracket body 20 that are inside the tooth model 16 areeliminated. Thus, the bracket body 20 is also shaped precisely accordingto the tooth surface and is equal to the surface of the pad. FIGS. 13Aand 13B show two bracket bodies that have had their surfaces 58 modifiedso as to conform to the surface of the tooth.

Next, using again a Boolean operation, the pad 18 and the body 20 areunited into one three-dimensional virtual object. An object representingthe sprue is placed on the bracket (for an embodiment in which thebracket is cast) and also united with the bracket model.

This process is done for each bracket. FIG. 14 shows 3D virtual modelsof a set of orthodontic brackets for the lingual treatment of the lowerarch.

A variation on the above method is as follows. First, the bracket bodyis retrieved from a library of bracket bodies and placed with respect tothe tooth surface in the correct position. Then, the tooth is“subtracted” from the bracket body+tooth object to delete the portion ofthe bracket body that would otherwise project into the tooth. A bracketbonding pad is created by assigning a thickness to a surface extractedor derived from the tooth surface, using the process described above forsurfaces 54. Then, the bracket body, as modified, is united to thebracket bonding pad.

Another possible embodiment is to use bracket bodies that are designedand stored in the computer which are as short as possible. Basically,these virtual bracket bodies would include the slot feature and littleor nothing else. The user would position the virtual bracket bodyadjacent to the virtual bracket bonding pad with a small gap formedbetween the bracket body and the bracket bonding pad. The bracketdesigning software includes a feature to generate a surface with asmooth transition between the bonding pad and the bracket body. Softwarethat provides functions to generate a smooth transition between twovirtual objects of arbitrary cross-section already exists, one examplebeing a 3D design program sold under the trademark Rhino3D™.

Another alternative and less preferred embodiment for manufacture ofcustomized bracket bonding pads would be to use standard bracket bodieswith standard bracket bonding pads, and then bend these pads to thedesired three-dimensional configuration using a bending robot. The wirebending robot in WO 01/80761 could be provided with different grippingfingers to grip a bracket and bend the tooth-facing surface of the padto fit the anatomy of the tooth. The opposite surface of the pad couldbe shaped by milling. Another embodiment would shape both tooth-facingside and the opposite side by milling.

Another aspect for selecting the appropriate bracket body for a giventooth is the extent of the malorientation of the tooth. For instance, atooth that is significantly angulated should be equipped with a widebracket bonding pad to provide satisfactory control, whereas a tooththat does not require a change in angulation could receive a very narrowbracket bonding pad since no angulation moment needs to be incorporatedinto the tooth.

Thus, from the foregoing discussion, it will be appreciated that avariety of methods for designing and manufacturing the brackets of thepresent invention are contemplated. Still others may be selected bypersons skilled in the art. The process of designing brackets occurs forall the required teeth in the arch and the process is performed for theopposing arch if desired.

The 3D models of the finished customized brackets in STL format areexported and fed into a wax printer. Such a wax printer is designedsimilar to an inkjet printer and builds up the object in a large numberof thin layers. The bottom layer is “printed” first: a fine jet blowsliquid wax onto a base plate. The portions that are part of the objectto be fabricated are printed using a wax with a high meltingtemperature. The remaining portions are filled with a wax of a lowmelting temperature. Then, the surface of the first layer is milled toreceive a planar layer of a precisely defined thickness. Afterwards, allfurther layers are applied in the same manner. After this is complete,the low-melting portions are removed by exposing them to a heatedsolvent.

The wax models of all brackets are then embedded in cement, making surethat the sprue is not completely covered. After the cement is hardened,the mold is heated, so that the wax cores are removed, and cavities arecreated. A gold-based alloy is cast into the mold. Then the mold isdestroyed, and the brackets are ready for use after removal of thesprue.

The resulting customized brackets could be bonded one by one, but it ismore efficient to place them onto a plaster model of the malocclusion,fixing them with a drop of liquid wax or a water soluble adhesive, andto overmold the complete set with silicone, thus creating a brackettransfer tray.

Obviously, a transfer tray according to OraMetrix's method of using anSLA representation of dentition plus brackets described in WO 01/80761,could also be used.

After the process of designing brackets is done for the entire arch, theposition of the bracket slots for the entire arch is stored as a fileand exported to a wire bending robot for bending of an archwire. Tomanufacture the wires, a six-axis-robot as described in WO 01/80761 isappropriate and a preferred embodiment. Since the location andorientation of each bracket is known and therefore the location andorientation of each slot, it is possible to generate robot controlfiles, containing the spatial information on each slot, and to use thesecontrol files to bend a wire having the configuration shown in FIG. 1.

The Magics™ software program allows the user to export co-ordinatesystems of individual objects in a proprietary file format. These areASCII files with the extension UCS. Such a file can be imported intoconversion software and turned into the CNA format used by the robot inWO 01/80761, which holds transformation matrices in binary format.Obviously, if the complete process of virtual set-up and virtual bracketdesign and placement would be performed within the native software ofthe wire bending system, such a conversion would not be required, as CNAfiles would be directly generated.

FIG. 15A shows prior art lingual brackets in which the straight wireapproach is used. Note the large size of the brackets. This results inmuch discomfort for the patient, articulation problems, and otherproblems as discussed previously. Compare FIG. 15A to FIG. 15B, a set ofbrackets provided in accordance with the teachings of this invention.The brackets are of a much reduced thickness. The advantages of thebracket and wire system of FIG. 15B has been set forth above.

Referring now to FIGS. 16-21, a presently preferred process of mergingthe bracket body 20 with the bracket bonding pad 18 in the computer willnow be described. FIG. 16 shows the combination of a virtual bracketbody 20 and virtual bracket bonding pad 18 during an intermediate stepin the design of a customized orthodontic bracket, in which the pad 18and bracket body 20 are two independent three-dimensional virtualobjects which can be moved relative to each other. In the situationshown in FIG. 16, the slot 22 is positioned relative to the pad 18 wherethe user wants it, but the portion 60 of the bracket body is projectingbeyond the tooth contact surface 24 of the pad, which is an undesirableresult.

FIG. 17 shows the screen of a computer workstation implementing thebracket design features described herein, in which the user is unitingthe pad and bracket body of FIG. 16 into a single virtual object. Thepad 18 is represented as a red object on the workstation user interfaceand the bracket body is a green object. The Magics™ software provides aunite icon, indicated at 62. When the user clicks OK at 64, the twoobjects 20 and 18 are united into one virtual 3D object. FIGS. 18A and18B are two views of the pad and bracket body combined as a singlevirtual object.

Next, the tooth object is recalled and the bracket body/pad object issuperimposed on the tooth. FIG. 19 shows the pad 18 and bracket body 20of FIGS. 18A and 18B placed on a virtual tooth 16.

Now, the portion 60 (FIG. 18) needs to be removed from the bracket. FIG.20 shows the screen of a computer workstation performing a subtractionprocess to subtract the tooth object 16 represented in red on theworkstation from the bracket bonding pad/bracket body 18/20 object,rendered in green on the workstation. This step is needed to remove theportion of the bracket body 60 that would otherwise project inside thetooth. The user activates the icon 66 indicating subtraction of the red(tooth) from the green (bracket pad/body) and clicks “OK.”

FIGS. 21A and 21B are two views of the bracket pad/bracket body objectafter the subtraction operation of FIG. 20 has been performed. Bycomparing FIG. 17 with FIG. 22, it will be seen that the portion 60 ofthe bracket body that would have otherwise projected within the toothhas been deleted from the bracket pad/bracket body object and thetooth-facing surface 24 conforms exactly to the surface of the tooth.

As noted above, it would be possible to space a virtual bracket bodyfrom a virtual bracket bonding pad in a desired spatial relationshipwith respect to each other and fill in the volume of space between thetwo objects with a suitable graphics tool, such as the Rhino3D program,to thereby unite the bracket body with the bracket bonding pad.Alternatively, the bracket body could be fit exactly to the bracketbonding pad using 3D graphics software tools without requiring anyportion of the bracket body to be removed. In this situation, the twovirtual objects intersect in a manner that the bracket body wouldpenetrate the pad only (e.g., a depth of intersection of the bracketbody and the bracket bonding pad of say 0.1 mm). Alternatively, the twoobjects could be united as described above and the portion that wouldotherwise project inside the tooth is removed as shown in FIGS. 16-21.

The archwires to be used with this invention can be of any suitablearchwire material known in the art or later developed. It has been foundthat relatively soft, heat treatable alloys are particularly suitable.It has been discovered that such wires are also ideal for bending with awire bending robot. One such alloy is a cobalt chromium alloy sold underthe trademark BLUE ELGILOY™, available from Rocky Mountain Orthodontics.This particular wire material has a composition of 40% cobalt, 20%chromium, 15% nickel, 7% molybdenum, 2% manganese, 0.15% carbon, balanceiron. A similar alloy is available from Ormco, sold under the trademarkAZURLOY™. These materials, along with others known to those skilled inthe art including nickel titanium, are particularly well suited for thesix-axis wire bending robot with heated gripper fingers described in WO01/80761. Such soft alloys are particularly desirable for lingualtreatment. Also, significantly, such alloys require very littleoverbending to achieve the desired bend in the wire, which isparticularly advantageous from a wire bending point of view sinceoverbending of wires to achieve the desired shape of the wire afterbending is complete is a difficult process to control exactly.

The wire can be heat treated after bending to increase the strength ofthe wire. The heat treatment can be provided by the robot grippingfingers using resistive heating techniques, immediately after eachsection of the wire is bent, using the techniques described in WO01/80761. Alternatively, the heat treatment can be performed afterbending the entire wire by placing the wire in an oven, or,alternatively the wire can be placed in a wire heating apparatusdescribed in U.S. Pat. No. 6,214,285. The temperature for heat treatmentis approximately 500 degrees F. The purpose of heat treatment of thewire here, to give the wire additional strength, is different from thepurpose of heat treatment of NiTi and other shape memory wires describedin WO 01/80761. The heat treatment of NiTi wires is needed to have thematerial take on the configuration of the wire as bent by the robot,whereas cobalt chromium wire will take the bend even without heattreatment. Heat treatment the cobalt chromium wire is generally for thepurpose of increasing strength of the wire.

These relatively soft wires, particularly the cobalt chromium alloys,which require very little overbending, are especially suited for lingualorthodontic brackets and canted archwires as described herein. In onepossible aspect of the invention we provide a method of forming anarchwire with a wire bending robot in which the wire comprises a cobaltchromium alloy that is subsequently heat treated, for example by thewire gripping apparatus of the wire bending robot as described in WO01/80761. In another aspect a method for bending and heat treating anarchwire is provided, comprising the steps of supplying the archwire toa wire bending robot, bending the archwire with the wire bending robotto have a predetermined configuration for a particular orthodonticpatient, and heat treating the archwire while said wire is held by thewire bending robot. The archwire includes a cobalt chromium wire, butother alloys that require heat treatment after bending could be used,instead. The step of bending and heat treating could be provided bybending the archwire is bent in a series of bends and heating the wireafter performing each of the bends in the series of bends.

While presently preferred embodiments have been described withparticularity, variation from the preferred and alternative embodimentsis of course possible without departure from the spirit and scope of theinvention. For example, the designing of the brackets with the aid of acomputer has been described using the Magics™ software program in whichsurface elements of the bracket bonding pad, tooth and bracket body arerepresented as triangles. However, there are other acceptablemathematical techniques for representing arbitrary three-dimensionalshapes in a computer, including volumetric descriptions (IGES format),and Nonuniform Rational B Splines (NURB), that could be used. Whilerepresentation of surface elements using triangles (SLA format) workswell in this invention, software using NURBs such as QuickDraw3D™ couldbe used. NURB software offers a way of representing arbitrary shapeswhile maintaining a high degree of mathematical exactness and resolutionindependence, and it can represent complex shapes with remarkably littledata. The methods and software used in the preferred embodiment fordesigning the brackets in accordance with the invention represent one ofseveral possible techniques and the scope of the invention is notlimited to the disclosed methods.

As another example, the manufacturing techniques that are used formanufacture of the brackets and wires are not critical and can vary fromthe disclosed techniques.

The reference herein to archwires with a rectangular, square or similarcross-section is considered to encompass archwires that basically havethis cross-sectional form but have slightly rounded corners and as suchare not exactly of rectangular or square cross-section. Similarly, thereference to the appended claims of an archwire having a flat planarside is intended to cover an archwire that basically has a flat planarside, notwithstanding a rounded of the corner from one face of the wireto another face.

Note, this invention is related to U.S. patent application Ser. No.10/897,149, by Wiechmann et al, “titled Modular System for CustomizedOrthodontic Appliances,” filed on Jul. 22, 2004, which claims thebenefit of and priority to application Ser. No. 10/075,676, now U.S.Pat. No. 6,776,614, all incorporated by reference herein in theirentirety.

This true spirit and scope of the invention will be understood byreference to the appended claims.

What is claimed is:
 1. A custom orthodontic bracket system comprising: abracket body having a bracket slot; a bracket bonding pad including atooth-facing surface and a surface opposite the tooth-facing surface forbonding the bracket body to a specific 3-dimensional surface of a toothof a predetermined patient, wherein the tooth-facing surface includes acontour that is a negative of and matches the 3-dimensional surface ofthe predetermined patient's tooth, and the opposite surface includes acontour that also matches and is a negative of the 3-dimensional surfaceof the patient's tooth; and an archwire positioned in the bracket slotforming a bracket slot-archwire interface and having a firstcross-sectional dimension and a second cross-sectional dimensionperpendicular to the first cross-sectional dimension, wherein a surfaceof the archwire or a major axis of the cross-section of the archwire isoriented substantially parallel to the predetermined patient's toothsurface.
 2. The custom orthodontic bracket system of claim 1, whereinthe bracket bonding pad covers portions of the cusps of the tooth. 3.The custom orthodontic bracket system of claim 2, wherein thetooth-facing surface contour and the opposite surface contour arederived from one or more digital representations of the tooth.
 4. Thecustom orthodontic bracket system of claim 1, wherein the bracketbonding pad covers a substantial area extent of the 3-dimensionalsurface of the tooth, wherein the substantial area extent is at least 50percent of the 3-dimensional surface.
 5. The custom orthodontic bracketsystem of claim 1, wherein the customized bracket body is linguallybondable to the teeth.
 6. The custom orthodontic bracket system of claim2, wherein the bracket is labially bondable to the teeth.
 7. The customorthodontic bracket system of claim 4, wherein the substantial areaextent is at least approximately 70 percent of the 3-dimensionalsurface.
 8. The custom orthodontic bracket system of claim 1, whereinthe tooth facing surface includes a metal or an alloy.
 9. The customorthodontic bracket system of claim 1, wherein the archwire includes anoval cross-section.
 10. A custom orthodontic bracket system comprising:Two or more customized brackets, each bracket having a bonding pad and abracket slot to be positioned adjacent the tooth surface, the bracketslot having a bracket slot width and a bracket slot height, wherein eachpad includes a tooth-facing surface and a surface opposite thetooth-facing surface, wherein both the opposite surface and the toothfacing surface includes a contour that is a negative of and matches the3-dimensional, lingual surface of a predetermined patient's tooth thatis covered by the pad, wherein the pad covers at least 50 percent of the3-dimensional surface, and wherein the tooth facing surface includes ametal or an alloy.
 11. The custom orthodontic bracket system of claim10, an archwire positioned in each bracket slot to thereby form abracket slot-archwire interface and having a first cross-sectionaldimension and a second cross-sectional dimension perpendicular to thefirst cross-sectional dimension, wherein a surface of the archwire or amajor axis of the cross-section of the archwire is orientedsubstantially parallel to each tooth surface.
 12. The custom orthodonticbracket system of claim 11, wherein the greater of the firstcross-sectional dimension or second cross-sectional dimension isoriented substantially parallel to the tooth surface.
 13. The customorthodontic bracket system of claim 11, further comprising an inlaypositioned between each bracket slot and the archwire.
 14. The customorthodontic bracket system of claim 13, wherein the inlay is U-shaped.15. The custom orthodontic bracket system of claim 11, wherein thearchwire is partially composed of heat treatable alloy.
 16. The customorthodontic bracket system of claim 10, wherein each bracket slots isoriented in parallel alignment relative to its respective bracketbonding pad.
 17. The custom orthodontic bracket system of claim 11,wherein the archwire includes a flat surface canted at an oblique anglerelative to the occlusal plane.
 18. The custom orthodontic bracketsystem of claim 10, wherein the pad covers at least 70 percent of the3-dimensional surface.
 19. The custom orthodontic bracket system ofclaim 10, wherein the bracket bonding pad covers portions of the cuspsof the tooth.
 20. The custom orthodontic bracket system of claim 10,wherein the tooth-facing surface contour and the opposite surfacecontour are derived from one or more digital representations of thetooth